Bipolar stimulator probes attachable to an electrical stimulator device or an electromyographic (EMG) device are commercially available for surface stimulation of peripheral nerves. Such apparatus provide both a stimulation electrode and a reference electrode on a single device. There are also bipolar bar electrode configurations, and sets of separate (individual) electrodes, for surface recording of nerve and muscle action potentials, and that can also serve to provide electrical muscle stimulation.
These types of devices can be used in surface stimulation for eliciting muscle twitches of the type sought in a muscle pain and discomfort relieving method developed by the present inventor, referenced herein as Surface Applied Electrical Twitch Obtaining Intramuscular Stimulation (SA-ETOIMS™). This methodology is described in U.S. provisional patent application Ser. No. 60/715,137, entitled “Intramuscular Stimulation Therapy Using Surface-Applied Localized Electrical Stimulation,” filed Sep. 9, 2005, and corresponding regular U.S. patent application Ser. No. 11/470,757, filed Sep. 7, 2006, which are hereby incorporated by reference in their entireties. This technique involves the provision of brief electrical stimulation at multiple motor end-plate zones (twitch-points) in many muscles. It is important that the stimulation method be “user friendly,” to both patient and treating clinician. That is, the stimulation should not cause significant additional discomfort to the patient and the method should be easy to apply for the clinician.
Commercially available standard bipolar stimulating probes have an inter-probe distance of 2 cm or less between the active and reference electrodes. This type of bipolar stimulation induces significant stimulation pain making it undesirable for use in the SA-ETOIMS™ procedure. In addition, due to the close proximity of the active and reference electrodes, twitches that may be elicited with such devices are small and have low forces, and therefore do not provide significant pain relieving effects. Similarly, as mentioned, surface electrodes that can be used for recording as well as stimulation purposes are available in the form of a bar electrode pair. Such devices have an inter-electrode distance of about 3-4 cm, and thus the same problem of inducing stimulation pain arises if these devices are used to perform SA-ETOIMS™. Stimulation/recording electrodes are also available as separate (individual) electrodes. However, separate individual electrodes are less than ideal for use in the SA-ETOIMS™ procedure, since both the active and reference electrodes have to be moved in bi-manual fashion to multiple stimulus and reference sites, thus slowing down and encumbering the SA-ETOIMS™ procedure and making the procedure more difficult for the clinician. These difficulties are alleviated to some extent by use of a monopolar stimulation tool, as is explained below.
The present inventor has performed SA-ETOIMS™ using monopolar stimulation, that is, with a generally pen-like tool having a single electrode mounted on its tip, which is used in conjunction with a separate reference electrode. Providing the stimulation electrode in the form of a stiff, pen-like tool gives the clinician a firm place to hold the tool in order to easily move the electrode to different stimulation sites in a rapid and efficient manner. The pain or discomfort relieving therapeutic effects are substantially achieved only when such sites with large force twitches are stimulated. SA-ETOIMS is performed in a time-based fashion, i.e. in incremental treatment segments of 10-15 minutes sessions to one hour sessions. For therapeutic effects to be substantial, it is essential that many large force twitch sites be sought, located and treated within the limits of timed sessions which are affordable and paid for by the patient as fee-for-service performed. To be able to search for as many large force twitch sites as possible within a given time-frame, the electrode needs to be moved to another site as soon as the twitch is elicited, i.e., within a fraction of a second. Therefore, it is crucial that the stimulation probes and reference electrodes allow expedient performance of the SA-ETOIMS procedure. However, a stimulation electrode provided in the form of a known-type adhesively applied disposable electrode has no firm place for the clinician to hold onto effectively, and is also impractical for efficient use in a treatment method involving electrode relocation every fraction of a second. The monopolar stimulation probe, similar in size and length to that of a pen, is very useful in SA-ETOIMS procedure and can be easily applied onto the skin surface for stimulation to evoke muscle twitches and to facilitate the search for large force twitch sites. However, the monopolar stimulation method requires use of a separate remote surface reference electrode, which is typically a known-type adhesively applied disposable electrode. The treatment is less painful than with bipolar stimulation with electrodes that are spaced 2-4 cm or less apart. However, monopolar stimulation has disadvantages.
With monopolar stimulation, moving the stimulating probe to different stimulus points has to be accompanied by relocating the disposable separate reference electrode to different body sites, multiple times, to avoid repetitive unnecessary stimulation and induced pain at the reference site. This type of surface reference electrode is not conducive to rapid movements, e.g., every second. Therefore, in practice, the electrode is moved after every minute or so. This bimanual work wastes time for the treating clinician since the disposable reference electrode will lose its adhesiveness, dislodge and/or fall off when subjected to multiple re-positioning and re-application onto the skin surface.
To avoid skin irritation from repetitive stimulation at one reference site only, and to avoid having to often move the single, separate reference electrode from place to place, several reference electrodes can be placed at different sites on the skin. By rotating the activation of different reference electrodes, there is better and more even distribution of the stimulus to different reference sites. This reduces the number of times any single reference electrode is subjected to removal and relocation. However, to activate a reference electrode placed at a different site, the clinician has to detach an alligator clip from the first reference electrode and re-attach it onto the next reference electrode with one hand, since the other hand holds onto the monopolar probe used for treatment. This creates inconvenience for the clinician since the alligator clip might not attach well when performed single-handedly. If bimanual attachment is required, it is disruptive to the treatment. It is also cumbersome since the multiple electrodes still need to be physically removed and rotated for placement at other skin sites to avoid discomfort at sites that have undergone previous repetitive stimulation. In prolonged treatments necessitating multiple different site placements of the reference electrodes, the electrodes can eventually lose their adhesiveness also causing them to fall off the skin surface. Additionally, when the reference electrode does not stick properly to the skin, the reduction in contact area of the reference electrode to the skin induces more treatment pain.
For optimal pain relieving results with SA-ETOIMS™, it is desirable to search for as many muscle motor points that can produce large force twitches as quickly as possible in a time-based treatment. Stimulation can be enhanced, and the yield of large force twitches made easier, when the surface reference electrode is placed at a distance from the stimulating probe. If the reference electrode is placed close to the stimulating probe, the treatment is painful and the twitches are small. The further the reference electrode is placed away from the stimulating probe, e.g., by as much 2-3 feet, the easier it is to elicit the sought-after large force twitches from deeply situated motor end plate zones (twitch-points). As one example, the reference electrode can be on the mid or low back region while stimulating calf muscles or arm muscles, but this creates a problem for the clinician if the reference electrode is at a site not within easy reach. The clinician then has to temporarily stop the treatment every time he/she has to reach over to the reference electrode or has to move closer to re-position the remote reference electrode to another location within reach.
Additional disadvantages of the monopolar stimulation approach (with separate reference electrode) include the fact that the lengthy separated wires of the stimulating and reference electrodes tend to get tangled, requiring that the clinician stop the treatment to untangle the wires. Additionally, there is a difficulty in finding a suitable site for reference electrode placement on the ventral (front) surface of the body where the skin is more sensitive to electrical stimulation, especially those associated with repetitive stimulation to one site. Also, if the clinician forgets to remove the reference electrode from the back of the body while treating muscles on the front of the body or the chest, a trans-thoracic current may be induced and adversely affect heart rhythm.